A power amplifier includes driver stages, where each driver stage supplies excitation to a next driver stage. Each driver stage consumes power to operate. The power consumed by the driver stages, however, reduces the power added efficiency of the power amplifier.
There are known techniques for improving the power added efficiency of a power amplifier. According to one known technique, the bias point, output matching network, or harmonic terminations of a power amplifier may be adjusted to decrease the DC power of the output stage of the amplifier. Decreasing the output stage DC power by matching to an efficiency load target may increase power added efficiency. According to another technique, the size of the driver stages may be reduced to minimize the power consumed by the driver stages. Minimizing power consumption by the driver stages may increase power added efficiency. Reducing the drive stage size, however, may not work for low output power amplifiers. The input stage for a low output power amplifier may be required to be extremely small, and extremely small stages are difficult to match.